This application proposes a five-wave study. with a longitudinal sample of 400 children and parents from African-American, Hispanic, and Caucasian families. Child participants will be drawn from a general school population on the basis of teacher ratings of temperament; participants will be oversampled from the highest 30 percent on the temperament-risk distribution and randomly drawn from the other 70 percent of the distribution. Participating families will initially be interviewed at child's age 9 years, and followed with repeated assessments through age 13 years (total of 5 assessments). The study will test a temperament model of early vulnerability and protection for substance use. Major propositions are that early onset is attributable to a combination of temperament and parental factors, and (within individuals) to the balance of activation and inhibition systems. The research will include constructs from epigenetic theory, social perception theory, and attitudinal theory. Basic data will be collected through interviews in homes, conducted with the child and a primary caregiver; data will also be obtained from a secondary caregiver, through ratings by school teachers, and from school records. Predictor variables include temperament dimensions, measures of behavioral activation and inhibition systems, and self-control constructs. Other measures include parental variables (support, self-control, marital relationship, religiosity, substance use, symptomatology), social integration, attachment, academic involvement, norms and attitudes about substance use, prototype perceptions and peer group characteristics, alternative reinforcers, and negative life events. Criterion variables will include tobacco, alcohol, and marijuana use, mental health indices, and measures of antisocial behavior. Data analysis will focus on structural modeling analysis and latent growth modeling to test predicted relationships between variables and determine variables that predict initial intercepts and growth over time in substance use. Latent transition analyses will be used to characterize sequences of onset. The results will have implications for the understanding of early onset of substance use and the design of prevention programs for children.